1. Field of the Invention
The present invention relates to telecommunications and, more particularly, to a system and method for controlling how services are provided to multi-mode mobile stations.
2. Description of Related Art
There is an increased interest in using more diverse types of wireless access technologies for mobile devices. Different wireless access technologies may be used to provide wireless coverage in different geographic areas. In addition, different wireless access technologies may be used to provide different capabilities for transmitting and receiving voice, data, and/or other media. For example, wireless wide area networks (WWANs), which often use wireless access technologies such as CDMA, TDMA, or GSM, typically provide wireless coverage in relatively large geographic areas. However, in many cases, WWANs do not provide good wireless coverage in buildings. In addition, many WWANs have a relatively limited bandwidth for transmitting and receiving media. However, wireless local area networks (WLANs), which may use wireless access technologies, such as IEEE 802.11, Bluetooth, HiperLAN, or HomeRF, have been used to provide wireless coverage in more limited areas, such as the inside of buildings. In addition, WLANs can often transmit and receive media at a higher rate than many WWANs.
With this increased interest in using diverse wireless access technologies to provide wireless coverage has come an increased interest in providing multi-mode mobile stations that can communicate using more than one type of wireless access technology. For example, a multi-mode mobile station may have one interface for communication with a WWAN, using a wireless access technology such as CDMA, and another interface for communication with a WLAN, using a wireless access technology such as IEEE 802.11. When the multi-mode mobile station uses the WWAN to send or receive calls, the voice or other media for the call may be carried in a circuit-switched network, e.g., in a time domain multiplexed (TDM) format. When the multi-mode mobile station uses the WLAN to send or received calls, the voice or other media for the call may carried in a packet-switched network in a voice over Internet Protocol (VoIP) format.
Although such multi-mode mobile stations can provide better wireless communication in more areas by being able to communicate over different wireless networks, a number of challenges remain. In particular, many subscribers are accustomed to being able to use various “enhanced” services or features when communicating with the WWAN. Such services may include, for example, “Class 5 features,” such as abbreviated dialing, call forwarding, call termination screening, three-way calling, voice mail, etc., as well as other services. In the WWAN, such services are often provided by the serving mobile switching center (MSC). To provide such services, the MSC may execute service logic that has been provisioned into the MSC. Alternatively, the MSC may query a service control point (SCP) in which the service logic has been provisioned. The SCP then executes the appropriate service logic and provides a response that instructs the MSC how to provide the service. This latter approach is often described as the “Wireless Intelligent Network” (WIN) approach and is described in TIA/EIA/IS-771, published in July 1999, which is incorporated herein by reference.
However, a different approach may be taken to provide services via a WLAN. For example, the IP Multimedia Subsystem (IMS) architecture has been proposed to define a service architecture that supports VoIP services. The IMS approach is described in a number of technical specifications of the 3rd Generation Partnership Project (3GPP), including TS 23.218 version 6.2.0 (2004-09), TS 23.228 version 5.12.0 (2004-03), and TS 24.229 version 6.4.0 (2004-09), which documents are incorporated herein by reference. In the IMS approach, services are provided by a call session control function (CSCF) in accordance with service logic provisioned in an application server.
Thus, although a multi-mode mobile station may be able to communicate with different wireless networks, the services provided to the multi-mode mobile station may differ for different types of wireless networks. Accordingly, there is a need for a unified approach for providing services to multi-mode mobile stations, for example, to apply services in a consistent fashion when a multi-mode mobile moves from a WWAN to a WLAN or vice versa.